From patchwork Sat Dec 5 05:21:55 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 338802 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-20.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81D63C4361B for ; Sat, 5 Dec 2020 05:22:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4A5FE22D2B for ; Sat, 5 Dec 2020 05:22:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725770AbgLEFWn (ORCPT ); Sat, 5 Dec 2020 00:22:43 -0500 Received: from mail.kernel.org ([198.145.29.99]:57540 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725730AbgLEFWn (ORCPT ); Sat, 5 Dec 2020 00:22:43 -0500 Date: Fri, 04 Dec 2020 21:21:55 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1607145716; bh=mgHX+8Us9feriapGknz720sjPjEF7uSvI4qm0A1mLgI=; h=From:To:Subject:From; b=xQhbZ3VE9tPto2gZDvzBJDvYB5SdfFa7ZitWLl6UgAeuv61altZOWhFUuQRywCBQy 8gG/L53TidJWmziWUbLq0hpBIcQ6JCaV5va1EhT7T0i8bu2JMGZk5zBk3+tlSvqkEj qZINKowC1lkfRCAPNx9kGG9moSSIxjTYxofCYNXg= From: akpm@linux-foundation.org To: adobriyan@gmail.com, andreyknvl@google.com, aryabinin@virtuozzo.com, catalin.marinas@arm.com, dvyukov@google.com, ebiederm@xmission.com, elver@google.com, glider@google.com, miles.chen@mediatek.com, mm-commits@vger.kernel.org, song.bao.hua@hisilicon.com, stable@vger.kernel.org, vincenzo.frascino@arm.com, will@kernel.org Subject: [to-be-updated] proc-use-untagged_addr-for-pagemap_read-addresses.patch removed from -mm tree Message-ID: <20201205052155.chIVRd2g0%akpm@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: proc: use untagged_addr() for pagemap_read addresses has been removed from the -mm tree. Its filename was proc-use-untagged_addr-for-pagemap_read-addresses.patch This patch was dropped because an updated version will be merged ------------------------------------------------------ From: Miles Chen Subject: proc: use untagged_addr() for pagemap_read addresses When we try to visit the pagemap of a tagged userspace pointer, we find that the start_vaddr is not correct because of the tag. To fix it, we should untag the usespace pointers in pagemap_read(). I tested with 5.10-rc4 and the issue remains. Explanation from Catalin in [1]: : Arguably, that's a user-space bug since tagged file offsets were never : supported. In this case it's not even a tag at bit 56 as per the arm64 : tagged address ABI but rather down to bit 47. You could say that the : problem is caused by the C library (malloc()) or whoever created the : tagged vaddr and passed it to this function. It's not a kernel regression : as we've never supported it. : : Now, pagemap is a special case where the offset is usually not generated : as a classic file offset but rather derived by shifting a user virtual : address. I guess we can make a concession for pagemap (only) and allow : such offset with the tag at bit (56 - PAGE_SHIFT + 3). My test code is baed on [2]: A userspace pointer which has been tagged by 0xb4: 0xb400007662f541c8 === userspace program === uint64 OsLayer::VirtualToPhysical(void *vaddr) { uint64 frame, paddr, pfnmask, pagemask; int pagesize = sysconf(_SC_PAGESIZE); off64_t off = ((uintptr_t)vaddr) / pagesize * 8; // off = 0xb400007662f541c8 / pagesize * 8 = 0x5a00003b317aa0 int fd = open(kPagemapPath, O_RDONLY); ... if (lseek64(fd, off, SEEK_SET) != off || read(fd, &frame, 8) != 8) { int err = errno; string errtxt = ErrorString(err); if (fd >= 0) close(fd); return 0; } ... } === kernel fs/proc/task_mmu.c === static ssize_t pagemap_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { ... src = *ppos; svpfn = src / PM_ENTRY_BYTES; // svpfn == 0xb400007662f54 start_vaddr = svpfn << PAGE_SHIFT; // start_vaddr == 0xb400007662f54000 end_vaddr = mm->task_size; /* watch out for wraparound */ // svpfn == 0xb400007662f54 // (mm->task_size >> PAGE) == 0x8000000 if (svpfn > mm->task_size >> PAGE_SHIFT) // the condition is true because of the tag 0xb4 start_vaddr = end_vaddr; ret = 0; while (count && (start_vaddr < end_vaddr)) { // we cannot visit correct entry because start_vaddr is set to end_vaddr int len; unsigned long end; ... } ... } [1] https://lore.kernel.org/patchwork/patch/1343258/ [2] https://github.com/stressapptest/stressapptest/blob/master/src/os.cc#L158 Link: https://lkml.kernel.org/r/20201127050738.14440-1-miles.chen@mediatek.com Signed-off-by: Miles Chen Reviewed-by: Catalin Marinas Reviewed-by: Vincenzo Frascino Cc: Alexey Dobriyan Cc: Andrey Konovalov Cc: Alexander Potapenko Cc: Andrey Ryabinin Cc: Dmitry Vyukov Cc: Marco Elver Cc: Will Deacon Cc: Eric W. Biederman Cc: Song Bao Hua (Barry Song) Cc: [5.4+] Signed-off-by: Andrew Morton --- fs/proc/task_mmu.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/fs/proc/task_mmu.c~proc-use-untagged_addr-for-pagemap_read-addresses +++ a/fs/proc/task_mmu.c @@ -1599,11 +1599,15 @@ static ssize_t pagemap_read(struct file src = *ppos; svpfn = src / PM_ENTRY_BYTES; - start_vaddr = svpfn << PAGE_SHIFT; end_vaddr = mm->task_size; /* watch out for wraparound */ - if (svpfn > mm->task_size >> PAGE_SHIFT) + start_vaddr = end_vaddr; + if (svpfn < (ULONG_MAX >> PAGE_SHIFT)) + start_vaddr = untagged_addr(svpfn << PAGE_SHIFT); + + /* Ensure the address is inside the task */ + if (start_vaddr > mm->task_size) start_vaddr = end_vaddr; /*